1. Technical Field
The present invention relates to an intake manifold, and more particularly to an intake manifold including a plurality of intake pipes which are provided in line.
2. Related Art
A conventional intake manifold including a plurality of intake pipes which are provided in line so as to send air to an engine mounted on a vehicle through the intake pipes has been generally known (refer to, for example, Patent Literature 1; JP 2014-224480 A). The intake manifold disclosed in Patent Literature 1 includes the intake pipes each of which is provided with a main body formed of resin and an end pipe formed of resin, welded to a lower stream end side of the main body, and joined to the engine. Further, each of the end pipes includes a control valve for controlling a volume of air flow.
According to the above structure, when a weld portion of the main body and the end pipe is broken and separated due to a collision load applied to the intake pipe at a vehicle crash, the main body moves relative to the end pipe joined to the engine, so that peripheral parts (for example, a fuel hose) may be damaged by a weld fracture surface of the main body. As a measure against that, a structure to reinforce an outer periphery side of the weld portion of the main body and the end pipe by a metal holder is suggested. According to this measure, although there is no problem in terms of strength, weight and cost of the intake manifold are increased due to addition of parts. As another measure against that, the main body and the end pipe may be molded in one piece so as not to form the weld portion instead of forming the main body and the end pipe separately. According to this measure, installation accuracy of, for example, a control valve which is provided in each of the end pipes is decreased. Further, because a shape of each of the intake pipes must be specialized, a complex construction of a metal mold with, for example, a rotational core is required, which may result in an increase of manufacturing cost.
Incidentally, in a technique disclosed in Patent Literature 2 (JP 2012-197702 A), an intake manifold includes a weld portion which is provided at an upper stream side of an intake pipe and whose direction is parallel to a load application direction in order to restrain the intake manifold from harming a fuel system at the vehicle crash. However, the technique disclosed in Patent Literature 2 is not applied to the intake manifold presupposing that the weld portion is provided at a lower stream side of each of the intake pipes.